Moving picture coding apparatus

ABSTRACT

A moving picture coding apparatus divides a picture into basic blocks and generates a prediction image of a block to be predicted in a basic block by using adjacent pixels in reference pixel blocks adjacent to the block to be predicted as reference pixels to perform predictive coding of a moving picture. When some of the reference pixels are not available, pixel values of the reference pixels that are not available are calculated based on pixels in the reference pixel blocks. The prediction image of the block to be predicted is generated by using the calculated pixel values instead of the reference pixels that are not available.

FIELD OF THE INVENTION

The present invention relates to a moving picture coding apparatus; andmore particularly, to a moving picture coding apparatus capable ofincreasing prediction accuracy when intra- or inter-prediction isperformed in pixel blocks based on the standards such as MPEG-2 andH.264.

BACKGROUND OF THE INVENTION

Nowadays, the amount of data transmitted in the form of a moving pictureis increasing day by day. For example, let's consider the amount of dataof an analog television. Currently, in the case of digitizing Japanesestandard television broadcasting, the number of pixels is 720 in ahorizontal direction and is 480 in a vertical direction. Each pixel hasa luminance component of 8 bits and two chrominance components of 8bits. A moving picture has stage main body 30 frames per one second.Currently, since a data ratio of a chrominance component to theluminance component is 1/2, the amount of data for one second is720×480×(8+8×1/2+8×1/2)×30=124,416,000 bits and a transmission rate ofabout 120 Mbps is required.

Further, an optical fiber currently supplied as a home broadband has atransmission rate of about 100 Mbps and thus an image cannot betransmitted without compression. The amount of data of terrestrialdigital television broadcasting to replace in 2011 is known as 1.5 Gbps.Accordingly, a highly efficient compression technology may be regardedas one of technologies required in the future. Currently, H.264/AVC(hereinafter, referred to as H.264) is suggested as the standard of thehighly efficient compression technology. H.264 is the up-to-dateinternational standard of moving picture coding developed by the jointvideo team (JVT) commonly established in December, 2001 by the videocoding experts group (VCEG) of the international telecommunication uniontelecommunication standardization sector (ITU-T) and the moving pictureexperts group (MPEG) of the international organization forstandardization (ISO)/international electro-technical commission (IEC).

ITU-T recommendations were admitted in May, 2003. In addition, theISO/IEC/joint technical committee (JTC) 1 was standardized as MPEG-4part 10 advanced video coding (AVC) in 2003.

H.264 is characterized in that the same picture quality can be realizedby coding efficiency which is about twice as high as that of theconventional MPEG-2 and MPEG-4, that inter frame prediction,quantization, and entropy coding are adopted as a compression algorithm,and that H.264 can be widely used not only at a low bit rate of a mobiletelephone or the like but also at a high bit rate of a high vision TV orthe like.

In addition, the ITU-T recommendations can be downloaded from the URLstated in the following Non-Patent Document 1.

[Non-Patent Document 1] “ITU-T Recommendation H.264 Advanced videocoding for generic audiovisual services”, [online], November 2007,TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU [searched on Dec. 12,2008], the Internet <URL:http://www.itu.int/rec/T-REC-H.264-200711-I/en>

In order to describe problems to be solved by the present invention, aprediction method of H.264 will be simply described with reference toFIGS. 1 to 3B.

In H.264, intra-prediction 104 for generating an intra-prediction imagepredicted by using correlations within a picture and inter-prediction105 for generating an inter-prediction image predicted by usingcorrelations between pictures are performed. A difference between thegenerated prediction image and an input picture 101 is obtained, andorthogonal transform, e.g., discrete cosine transform (DCT), 102 andquantization (Q) 103 are performed on the differential data. Then,coding 110 is performed on the quantized data. In H.264, only thedifferential data is coded and transmitted, thereby realizing highcoding efficiency.

Here, the reference numeral 107 indicates a deblocking filterstandardized in H.264, and the reference numeral 108 is inverseorthogonal transform, e.g., inverse discrete cosine transform (IDCT),for performing an inverse processing to the processing of the orthogonaltransform 102. Further, the reference numeral 109 indicates inversequantization (IQ) for performing an inverse processing to the processingof the quantization 103. The filter 107, the inverse orthogonaltransform 108 and the inverse quantization 109 perform the processing toobtain reconstructed pictures in an encoder. The reconstructed picturesfor a plurality of previous frames are stored in a frame memory 106 andare retrieved to the inter-prediction 105.

The intra-prediction generates the prediction picture based on acorrelation between adjacent pixels. In the intra-prediction, theprediction picture is generated by using correlations between a pixel tobe predicted and its adjacent pixels, wherein pixels in a left columnand an upper row of a block to be predicted are used. In FIG. 2, forexample, reference pixels used for generating a prediction picture of4×4 intra-prediction are illustrated.

In H.264/AVC, it is possible to generate prediction pictures on a basisof block of 4×4 pixels (hereinafter, referred to as 4×4 block), 8×8pixels (hereinafter, referred to as 8×8 block), or 16×16 pixels(hereinafter, referred to as 16×16 block). As available modes, total 22modes (9 modes in 4×4 blocks, 9 modes in 8×8 blocks and 4 modes in 16×16blocks) can be used.

The intra-prediction modes of H.264/AVC in the respective blocks areillustrated in the following Table 1.

TABLE 1 Intra-prediction Modes Intra 4× process chamber 4/Intra 8 × 8Intra 16 × 16 0 Vertical 0 Vertical 1 Horizontal 1 Horizontal 2 DC 2 DC3 Diagonal Down Left 3 Plane 4 Diagonal Down Right 5 Vertical Right 6Horizontal Down 7 Vertical Left 8 Horizontal Up

In the modes 0 and 1, prediction is performed by using adjacent pixels.It is possible to obtain high prediction efficiency for blocks includingvertical edges and horizontal edges. In the mode 2, an average value ofadjacent pixels is used. In the modes 3 to 8, a weight average isobtained from every 2 to 3 pixels from adjacent pixels and is used as aprediction value. It is possible to obtain a high prediction effect forimages including edges of 45 degrees to the left, 45 degrees to theright, 22.5 degrees to the right, 67.5 degrees to the right, 22.5degrees to the left, and 112.5 degrees to the right, letting thevertically downward direction be 0 degree. In H.264, it is possible torealize highly efficient coding by selecting a proper mode from theintra-prediction modes of the images. In general, rough intra-predictionis performed to select an optimal intra-prediction mode.

In addition, although not described in detail herein, in theinter-prediction that is defined in H.264/AVC, a motion vector of apixel to be predicted is calculated from previous and future pictures tothereby generate a prediction picture.

The adjacent pixels referred to in the intra-prediction are A to Millustrated in FIG. 2. However, when a picture edge, a slice boundary,and reference pixels are coded by the inter-prediction, reference pixelsdo not exist. Further, since reference beyond the slice boundary isprohibited, available modes are limited. In addition, in H.264, theintra-prediction is performed in the order of the numbers illustrated inFIGS. 3A and 3B.

The reference pixels used in the respective prediction modes areillustrated in the following Table 2.

TABLE 2 Prediction Modes and Available Reference Pixels Intra 4 × 4/Available Available Intra 8 × 8 Reference Pixels Intra 16 × 16 ReferencePixels 0 Vertical Upper 0 Vertical Upper 1 Horizontal Left 1 HorizontalLeft 2 DC Upper/Left 2 DC Upper/Left 3 Diagonal Upper/ 3 PlaneUpper/Left/ Down Left Upper Right Upper Left 4 Diagonal Upper/Left/ DownRight Upper Left 5 Vertical Upper/Left/ Right Upper Left 6 HorizontalUpper/Left/ Down Upper Left 7 Vertical Upper/ Left Upper Right 8Horizontal Left Up

As can be seen from the reference pixels used in Table 2, in the case ofthe 4×4 intra-prediction, since the pixels on the left/upper left do notexist at the picture edge, the modes 1, 4, 5, 6 and 8 cannot be used.Further, when the upper end of the block to be predicted is a sliceboundary, the modes 0, 3, 4, 5, 6 and 7 cannot be used since thereference pixels on the upper/upper right are outside the sliceboundary. In the case of the 8×8 intra-prediction, in the same way as inthe 4×4 intra-prediction, 9 intra-prediction modes are defined and modelimitations due to the pixels that cannot be referred to are the same asthose in the 4×4 intra-prediction. In the case of the 16×16intra-prediction, an available mode is the mode 4 and reference pixelsalso do not exist in case of a picture edge and the slice boundary andreference beyond the slice boundary is also prohibited.

Further, in other cases than the above, when the reference pixelsrequired in generating the prediction picture of the pixel block to bepredicted, i.e., adjacent pixel blocks, are coded by theinter-prediction (when constrained_intra_pred_flag is ‘1 ’ in H.264), itis defined that an intra-prediction picture cannot be generated withreference to such adjacent blocks.

As described above, when coding is performed based on a conventionalmethod, limitations on available modes are generated, therebydeteriorating the accuracy of the generated prediction picture. Further,a difference value between the prediction picture and an input pictureincreases due to the deterioration of the accuracy of the predictionpicture. As a result, in the coding 110 of FIG. 2, the amount of codesrequired for coding the blocks to be predicted, in which limitations onmodes are generated, increases.

In the range where a transmission band is limited, particularly, in lowbit rate transmission, an increase in the amount of generated codesaffects entire coding.

SUMMARY OF THE INVENTION

In view of the above, the present invention provides a moving picturecode compressing apparatus capable of compressing codes withoutincreasing the amount of generated codes, furthermore, withoutdeteriorating the accuracy of an image to be predicted when intra- orinter-prediction is performed in units of pixel blocks.

In the prediction performed by the moving picture coding apparatus inaccordance with the present invention, when some of reference pixels ina block to be predicted are not available, the pixels values of thereference pixels that are not available are calculated based on thepixels in the reference pixel block to generate a prediction picture ofthe block to be predicted by using the calculated pixel values insteadof the reference pixels that are not available.

Then, an average value of some pixels in the reference pixel block anddifference values thereof are obtained. The pixel values of thecorresponding reference pixels are obtained based on the obtainedaverage value and difference values.

In accordance with the embodiment of the present invention, it ispossible to provide a moving picture code compressing apparatus capableof compressing codes without increasing the amount of generated codes,furthermore, without deteriorating the accuracy of a prediction picturewhen intra- or inter-prediction is performed in pixel blocks.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become apparentfrom the following description of preferred embodiments, given inconjunction with the accompanying drawings, in which:

FIG. 1 is a configuration diagram of an encoder of H.264;

FIG. 2 illustrates positions of reference pixels in generating anintra-prediction picture;

FIGS. 3A and 3B illustrate the order of intra-prediction in a block inH.264;

FIG. 4 illustrates a relationship between a reference pixel block and ablock to be predicted;

FIG. 5 illustrates a relationship between a pixel line used for paddingand pixels (in a horizontal direction) to be padded in accordance withan embodiment of the present invention;

FIG. 6 illustrates a relationship between a pixel line used for paddingand pixels (in a vertical direction) to be padded in accordance with theembodiment of the present invention;

FIG. 7 illustrates the outline of a padding algorithm in imageprediction in accordance with the present invention;

FIG. 8 is a flowchart illustrating the flow of padding when upperreference pixels are not available;

FIG. 9 illustrates a reference pixel block and a block to be predictedwhen the upper reference pixels are not available;

FIG. 10 illustrates that the reference pixels are padded in thehorizontal direction (step 1) in the relationship between the referencepixel block and the block to be predicted of FIG. 4;

FIG. 11 illustrates that the reference pixels are padded in thehorizontal direction (step 2) in the relationship between the referencepixel block and the block to be predicted of FIG. 4;

FIG. 12 illustrates that the reference pixels are padded in thehorizontal direction (step 3) in the relationship between the referencepixel block and the block to be predicted of FIG. 4;

FIG. 13 illustrates that the reference pixels are padded in thehorizontal direction (step 4) in the relationship between the referencepixel block and the block to be predicted of FIG. 4;

FIG. 14 is a flowchart illustrating the flow of padding when leftreference pixels are not available;

FIG. 15 illustrates a reference pixel block and a block to be predictedwhen the left reference pixels are not available;

FIG. 16 illustrates that the reference pixels are padded in the verticaldirection (step 1) in the relationship between the reference pixel blockand the block to be predicted of FIG. 4;

FIG. 17 illustrates that the reference pixels are padded in the verticaldirection (step 2) in the relationship between the reference pixel blockand the block to be predicted of FIG. 4;

FIG. 18 illustrates that the reference pixels are padded in the verticaldirection (step 3) in the relationship between the reference pixel blockand the block to be predicted of FIG. 4;

FIG. 19 illustrates a data hierarchy in H.264;

FIG. 20 illustrates an access unit in H.264;

FIG. 21 illustrates an example of an access unit, in which padding isset in the image prediction in accordance with the present invention;

FIG. 22 illustrates a pixel block, in which limitations on modes aregenerated by a slice boundary/picture edge in conventional H.264; and

FIG. 23 illustrates a pixel block, in which limitations on modes aregenerated by using adjacent pixels in inter-prediction of theconventional H.264.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present invention will be describedwith reference to FIGS. 4 to 23 which form a part hereof.

In accordance with the embodiment of the present invention, in a datacompressing process performed by a moving picture coding apparatus, whenimage prediction is performed, data on the pixels that cannot bereferred to due to the position conditions of a block to be predictedare padded so as to be used as the reference pixels of the block to bepredicted.

To be more specific, in accordance with the present invention, ingenerating a prediction image, when upper or left reference pixels areavailable and pixels on the other side are not available, even if thepixels at a picture edge and at a slice end or adjacent pixels are codedby inter-prediction by performing padding based on a pixel average and apixel difference using the available reference pixel blocks, properreference pixels are generated regardless of limitations on theprediction generated by prediction image generation modes. Therefore,when the upper or left reference pixels are available, all of the modesare available even for the pixels at the picture edge and on the sliceboundary, so that a highly dense prediction image can be generated. Inthis way, in accordance with the embodiment of the present invention, adifference between the prediction image and an input image is reduced tothereby improve coding efficiency.

Hereinafter, the outline of padding in the prediction of the movingpicture coding apparatus in accordance with the present invention willbe described with reference to FIGS. 4 to 7.

In accordance with the embodiment of the present invention, when anupper or left reference pixel block of the block to be predictedillustrated in FIG. 4 cannot be referred to, one reference pixel blockis padded from the other reference pixel block.

More specifically, as illustrated in FIGS. 5 and 6, padding is performedby using the available reference pixel lines 501 and 601 closest topixels 502 and 602 to be padded. Here, pixels to be padded in ahorizontal direction and a pixel line required for performing paddingare illustrated in FIG. 5, and pixels to be padded in a verticaldirection and a pixel line required for performing padding areillustrated in FIG. 6.

The basic padding in the image prediction in accordance with theembodiment of the present invention is to generate pixels 705 to bepadded from a padding reference pixel line 704 illustrated in FIG. 7.First, a pixel average value 701 of the padding pixel line is obtained.Next, differences 702 between the respective pixel values and the pixelaverage value 701 are obtained. Then, a padding reference pixel 703 ofthe pixel to be padded is determined. Based on the padding referencepixel 703, at the respective pixels to be padded, the padding referencepixel 703 and the differences 702 are added to obtain final values ofthe pixels to be padded. In FIG. 7, the padding in the horizontaldirection is illustrated. When the padding in the vertical direction isperformed, the reference pixel line and the pixels to be padded arearranged in the vertical direction.

Hereinafter, the padding in the image prediction of the moving picturecoding apparatus in accordance with the embodiment of the presentinvention will be described in detail with reference to FIGS. 8 to 18.

Also in this embodiment, in the same way as in H.264/AVC,intra-prediction is performed in the order of the numbers illustrated inFIGS. 3A and 3B. Further, in this embodiment, 4×4 intra-prediction willbe taken as an example. In a padding method of the image prediction inaccordance with the embodiment of the present invention, the padding isperformed by using a macroblock including available reference pixels, apixel average, and a pixel difference. The padding can be also performedin an 8×8 block and in a 16×16 block by using the same method as in the4×4 block described in this embodiment.

First of all, padding in a case where upper pixels of FIG. 9 cannot bereferred to will be described.

First, as illustrated in FIG. 10, an uppermost reference pixel I of left4 pixels is copied to the position of a reference pixel M (step 1 ofFIG. 8).

Next, an average value Ave(i_1 to i_4) of the pixel values in theuppermost horizontal line (i_1 to i_4 of FIG. 11) of a left referencepixel block is calculated by the following Eq. 1 (step 2):

$\begin{matrix}{{{{Ave}( {{i\_}1\mspace{14mu} {to}\mspace{14mu} {i\_ N}} )} = \frac{\sum\limits_{i = 1}^{N}{{pixel}\mspace{14mu} {value}\mspace{14mu} {Xi}}}{N}},} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

where N=4 in this example.

Then, differences ΔAve(i_1 to i_4, i_x) between the respective pixels inthe uppermost horizontal line of the reference pixel block and theaverage value obtained by Eq. 1 are calculated by the following Eq. 2:

$\begin{matrix}{{{\Delta \; {{Ave}( {{{i\_}1\mspace{14mu} {to}\mspace{14mu} {i\_ N}},{i\_ x}} )}} = {{i\_ x} - \frac{\sum\limits_{i = 1}^{N}{{pixel}\mspace{14mu} {value}\mspace{14mu} {Xi}}}{N}}},} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

where N=4 in this example.

Subsequently, the differences of Eq. 2 are added to the pixel value ofthe copied reference pixel M to pad resultant values to the respectivecorresponding positions as the values of the upper reference pixels(step 3). In FIG. 12, an example of padding a reference pixel A isillustrated.

In a block to be predicted, upper right reference pixels are notavailable at the positions of 1, 3, 4, 5, 7, 11, 13, and 15 illustratedin FIG. 3A. Accordingly, the pixel values of EFGH cannot be predicted inview of the standards. Therefore, as illustrated in FIG. 13, the pixelvalue of the rightmost pixel D of the upper reference pixels is copiedto set it as EFGH (step 4).

The upper reference pixels are padded by the processes of steps 1 to 4.Since the reference pixels become available, a prediction image isgenerated by all of the modes using the upper reference pixels as“available for Intra_(—)4×4 prediction”.

Next, padding in a case where left pixels of FIG. 15 cannot be referredto will be described.

First, as illustrated in FIG. 16, the leftmost reference pixel A ofupper 4 pixels is copied to the position of the reference pixel M (step11 of FIG. 14).

Then, an average value Ave(a_1 to a_4) of the pixel values (a_1 to a_4of FIG. 17) in the leftmost vertical line of an upper reference pixelblock is calculated by the following Eq. 3 (step 12 of FIG. 14):

$\begin{matrix}{{{{Ave}( {{a\_}1\mspace{14mu} {to}\mspace{14mu} {a\_ N}} )} = \frac{\sum\limits_{i = 1}^{N}{{pixel}\mspace{14mu} {value}\mspace{14mu} {Xi}}}{N}},} & {{Eq}.\mspace{14mu} 3}\end{matrix}$

where N=4.

Next, in this example, differences ΔAve(a_1 to a_4, a_x) between thepixel values in the leftmost vertical line of the reference pixel blockand the average value obtained by Eq. 3 are calculated by the followingEq. 4:

$\begin{matrix}{{{\Delta \; {{Ave}( {{{a\_}1\mspace{14mu} {to}\mspace{11mu} {a\_ N}},{a\_ x}} )}} = {{a\_ x} - \frac{\sum\limits_{i = 1}^{N}{{pixel}\mspace{14mu} {value}\mspace{14mu} {Xi}}}{N}}},} & {{Eq}.\mspace{14mu} 4}\end{matrix}$

where N=4. Then, the differences are added to the pixel value of M topad resultant values to the respective corresponding positions of theleft reference pixels.

In FIG. 18, an example of padding a reference pixel I is illustrated.

The left reference pixels are padded by the processes of the above steps11 to 13. Since the left reference pixels become available, in the sameway as the padding of the upper reference pixels, a prediction image isgenerated by all of the modes using the reference pixels as “availablefor Intra_(—)4×4 prediction”.

Finally, a case where upper and left reference pixels of a block to bepredicted do not exist, e.g., a case of a first macroblock of a slice,will be described. In this case, in the same ways as the conventionalH.264 standard, a prediction image is generated by replacing all thepixel values of the block to be predicted by a median that is, e.g., 512when an input format is 10 bits.

As described above, by performing the padding in accordance with theembodiment of the present invention, even when upper or left pixels of ablock to be predicted do not exist, it is possible to generate aprediction image by using all of the modes defined by H.264. Inaccordance with the embodiment of the present invention, since theaverage value and the pixel differences of the line closest to thepixels to be padded from the available reference pixel block are used,pixels available for prediction are reconstructed in the padded pixels.As a result, it is possible to generate a highly dense prediction image.

Next, a case where the padding of the image prediction described in thisembodiment is performed based on H.264 will be described with referenceto FIGS. 19 to 21.

In the bit stream structure of H.264, as illustrated in FIG. 19, anetwork abstraction layer (NAL) including NAL units 1703 and 1704 isdefined between a moving picture coding layer including coding data 1701and parameter set 1702 to perform moving picture coding and a lowersystem such as MPEG-2 system 1705 for transmitting and accumulatingcoded information. Thus, the bit stream to the lower system 1705 isperformed on a basis of NAL unit. In FIG. 19, the position of the NALunit in H.264 is illustrated.

In order to access information in the bit stream in units of pictures,several NAL units are arranged in an access unit. The structure of theaccess unit is illustrated in FIG. 20. An AU delimiter 1801 is a startcode that represents the head of the access unit. A sequence parameterset (SPS) 1802 is a header including information on coding of an entiresequence such as the profile and level of a primary coded picture (PCP)image. A picture parameter set (PPS) 1803 is a header that representsthe coding mode of an entire picture. A supplement enhanced information(SEI) 1804 is a header including certain additional information such astiming information of each picture and random access information. Aprimary coded picture (PCP) 1805 is an NAL unit consisting of at leastone slice data. A redundant coded picture (RCP) 1806, which is an NALunit including macroblock data such as PCP, is redundancy data that canbe used when PCP is lost by errors. An end of sequence (EOS) 1807 is apart that represents the end of a sequence. An end of stream (EOS) 1808is a part that represents the end of a stream. In H.264, it is definedthat the access unit includes the AU delimiter 1801 to the EOS 1808arranged in order.

When the padding of the image prediction described in this embodiment isperformed based on H.264, in the SPS 1802 illustrated in FIG. 20, a flagfor determining intra-padding is added. At a decoder, it is determinedwhether the intra-padding is to be performed or not based on the flagdetermination. The SPS 1802 is the header including the information onthe coding of the entire sequence such as the profile and level of thePCP image. In H.264, the final parameter of the SPS isvui_parameters_present_flag that represents whether the syntax structureof video usability information (VUI) that is a data structure related tovideo display information exists or not. After thisvui_parameters_present_flag, a flag of 1 bit that represents whether theintra-padding in accordance with the embodiment of the present inventionis to be performed or not is added.

As shown in FIG. 21, at the last part of the SPS 1802 of theconventional H.264, a padding determination flag 1900 related to thepadding of the image prediction described in this embodiment is added.When the decoder performs decoding, as in the conventional method, afterthe PSP 1803 is decoded, the padding flag information 1900 is decoded todetermine whether the padding is to be performed or not. The decoder canperform decoding by using a prediction image generation block, in thesame way as the encoder.

Finally, the advantages of the padding of the image prediction inaccordance with this embodiment will be described in comparison with themethod of the conventional H.264 with reference to FIGS. 22 and 23.

In the conventional H.264, the modes that can be used for generating theprediction image on the slice boundary and at the picture edge arelimited when the intra-prediction is used. For example, when 1 slice isset as a 1 macroblock line (16 lines) in the screen size of 1920*1080,in 4×4 pixel units, limitations on available modes are generated in theregion of about 25% in the uppermost 4×4 block and at the picture edgeas illustrated in FIG. 22. Similarly, mode limitations are generated inabout 50% in 8×8 pixel units and are generated in all of the macroblocksin 16×16 pixel units. However, in accordance with the embodiment of thepresent invention, since the padding cannot be performed only by thefirst macroblock of the slice, the medium values are processed. In theother macroblocks, since limitations on available modes do not exist ingenerating the prediction image, it is possible to generate a highlydense prediction image.

Further, when the prediction image is generated by using theintra-prediction and the inter-prediction, if the pixel block positionedin the reference pixel block is coded by the inter-prediction(constrained_intra_pred_flag=‘1’) as illustrated in FIG. 23, it isexpected that the pixel blocks, in which mode limitations are generated,further increase, in addition to the above situation. Therefore, thepresent invention is more effective.

While the invention has been shown and described with respect to theparticular embodiments, it will be understood by those skilled in theart that various changes and modification may be made.

1. A moving picture coding apparatus for dividing a picture into basicblocks and generating a prediction image of a block to be predicted in abasic block by using adjacent pixels in reference pixel blocks adjacentto the block to be predicted as reference pixels to perform predictivecoding of a moving picture, wherein when some of the reference pixelsare not available, pixel values of the reference pixels that are notavailable are calculated based on pixels in the reference pixel blocks,and wherein the prediction image of the block to be predicted isgenerated by using the calculated pixel values instead of the referencepixels that are not available.
 2. The moving picture coding apparatus ofclaim 1, wherein each of the pixel values of the reference pixels thatare not available is calculated based on a correlation of the pixels inthe reference pixel block.